MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - 1275 card leaking

Hi people, I wondered if anyone could give me advice...

I have a 1971 1275 midget leaded twin carb and am having trouble with the float chamber nearest the front of the car. I spotted petrol all over the top of the chamber...then dripping onto the ground. I replaced the hoses but it is still leaking. I noticed a thin metal plate around the metal connector where the hose attaches and it appears that the small hole (directly underneath the connector - covered by the thin plate)is where the petrol is coming from. I take it that this is a sort of breather?....anyone any idea what is going on and how to fix it?
Many thanks!
Mik

Yes it is a breather and should be there. When fuel comes from this hole it is because the carb is overfilling (floodiing) Generally because the needle valve in the float bowl is faulty. Try cleaning it or adjusting it as per the manual or equally the float itself maybe faulty and not closing the needle valve
Bob (robert) Midget Turbo

Bob has it right the hole lets excess fuel out if the needle valve is worn out or a dollop of grubble is stuck in the valve or when the float which should shut off the fuel flow sinks because it has begun leaking.

It is not difficult to investigate these possibilities, but do make sure you dont damage the gasket around the top of the float chamber when you separate the two parts by unscrewing the three screws

Look around the tip of the needle valve (the conical end) the most likely thing is that you will find a ring worn all around the tip which shows that fuel can no longer be shut off when the float rises to its proper level

New needle valves are cheap enough (many car spares shops still carry these on a "card on the wall" from the days when every boy racer had a Mini rather than a Jap-coffee-can sportster) The best have a viton (rubbery stuff) tip rather than the bare steel tip but it is more important to shut the fuel flow off than to say "my tip is better than your tip" in my opinion

Favoured brands from back in the day were Speedwell, these days the ones from the Rover Dealers recently were rubber tipped and I can reccommend them if you can get hold of one/two.

Dont forget the carbs will both have the same mileage, if one tip has worn badly, t'other isnt far away from the same wear pattern.

Burlen Fuel Systems are the makers and agents for SU carbs and spares and will sell you everything you need for an overhaul
Bill

Many many thanks for the replies guys...will take apart tommorrow(weather/work depending).
Have had a look at needles/seats etc...found WZX1101A in the moss cat'...hope it's the right one(year and CC match)....shouldn't say 'match' with all this expensive petrol about.

Will keep you updated!

Mik

*UPDATE*
Have taken said float apart...needle moves ok and does not appear to be worn...cleaned etc all parts...
However, having looked at pics of the float, there should be a metal plate for adjustment. This is missing(nowhere to be seen).
The car has been driving well for 18 months until now...it is a plastic float(not leaking)but there is a tiny bit of wear where the needle pushes into it.
Is this a new design? How do I get around this and is this a normal float?

Thanks
Mik

*FURTHER UPDATE* Upon further investigation(in the MOSS catalogue), these floats look like the ones from a 1500!
Is/was this normal practice? Could this be a problem?

Sorry for all the questions but it is really bugging me now :-(

Mik

you might have some dirt in the hole thats under the float needle.....try rapping the te side of the float bowl with a wrench and see if that does anything...if not...use a paperclip as a pipe cleaner for that little hole under the float needle...aka looks like a plume bob...

But most likely it will be an adjustment related
Prop

Many thanks, did that :-)
The main float chamber (nearest the rad) is no longer overflowing, after a little 'Bodge' approach. However, now the other float is doing the same...grrrrrr!!
Mik

HELP!
The main float chamber (nearest the rad) is no longer overflowing(managed to sort it)however, now the other float is doing the same and leaking from the breather hole.

Mik

Don't panic Mik - you sorted the first one, just apply the lessons learned to the second. Get in there and remove the needle, inspect and clean. You may want to remove the jet as well and ensure that's not blocked. What's happening is that the fuel pump will continue to pump fuel into that float chamber until the float needle is pushed up into the jet, and closes it off, by the float underneath. A tiny bit of crud / grit / rust (and it need only be teeny weeny) between the two will prevent a seal, the fuel keeps pumping, fills the chamber and floods out the vent on the top.

If it's only just started doing it, it's almost certainly the same cause as the first.

When you're happy they're both clear, install an inline cheap, clear plastic fuel filter - about £3.00 - 4.00 from your local motor factor. Sounds like you may have some crap in the fuel.
Steve Clark

This thread was discussed between 29/06/2008 and 03/07/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.